From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6675B223DDF; Mon, 23 Jun 2025 21:26:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750713979; cv=none; b=u7yAy66ObrYUKbyAq05vTiNb+LcCjGf3Yg1TZiL9VgWpo5D+loviv+a9qsg1K98ofTcF9zL2qAKBGPqxl7F5YQ+GjL3bknSBCI/CYvMfc+LIwAZ7UhQ8kVKnaSSY4uQwlbPrt0iK7Bp/Xf220lljGCItnVKPxfHCV4GB7zm1Fyg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750713979; c=relaxed/simple; bh=1VfBy5Ld9bBSPHmlOUlDYAB8oL0JrvzmiUg89TUoryA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=G2ThxHMc+fFQT7Cx8v8KihR9GtlhkSy0nb1ivsjtUgeUsZlGnunDTD+y2pxN8qcD4CX79ucRn0IRNeDsdXf0ROaeLb5pjtp//HkTURe9g+2rTQ2KFQkKR1RHQOA8reKymh1B01ex8lApMO2JAZUm9bcLvVuCE2IUEqaeI6WmNoQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=NplnlTDh; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="NplnlTDh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F2108C4CEEA; Mon, 23 Jun 2025 21:26:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1750713979; bh=1VfBy5Ld9bBSPHmlOUlDYAB8oL0JrvzmiUg89TUoryA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NplnlTDh04uGfC0FYfRPosqFQHtZEbNEM7kopkUnLpGmWBjUoeXLDYXFcke0oww+t eMd84jWFsy4CrfCnWgh4F49OiZhM1fGLhyD5hpRCv9EdHms23ysBZnHmJtuzmo8CR4 esxl8JMaCSbbA56bakoRD3RkxSsP8RWV2qozfbEo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Gerrard Tai , Eric Dumazet , Jakub Kicinski , Sasha Levin Subject: [PATCH 5.15 158/411] net_sched: prio: fix a race in prio_tune() Date: Mon, 23 Jun 2025 15:05:02 +0200 Message-ID: <20250623130637.624472552@linuxfoundation.org> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250623130632.993849527@linuxfoundation.org> References: <20250623130632.993849527@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit d35acc1be3480505b5931f17e4ea9b7617fea4d3 ] Gerrard Tai reported a race condition in PRIO, whenever SFQ perturb timer fires at the wrong time. The race is as follows: CPU 0 CPU 1 [1]: lock root [2]: qdisc_tree_flush_backlog() [3]: unlock root | | [5]: lock root | [6]: rehash | [7]: qdisc_tree_reduce_backlog() | [4]: qdisc_put() This can be abused to underflow a parent's qlen. Calling qdisc_purge_queue() instead of qdisc_tree_flush_backlog() should fix the race, because all packets will be purged from the qdisc before releasing the lock. Fixes: 7b8e0b6e6599 ("net: sched: prio: delay destroying child qdiscs on change") Reported-by: Gerrard Tai Suggested-by: Gerrard Tai Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20250611111515.1983366-2-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/sched/sch_prio.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/sched/sch_prio.c b/net/sched/sch_prio.c index 2e0b1e7f54668..b3defe09d9f7b 100644 --- a/net/sched/sch_prio.c +++ b/net/sched/sch_prio.c @@ -211,7 +211,7 @@ static int prio_tune(struct Qdisc *sch, struct nlattr *opt, memcpy(q->prio2band, qopt->priomap, TC_PRIO_MAX+1); for (i = q->bands; i < oldbands; i++) - qdisc_tree_flush_backlog(q->queues[i]); + qdisc_purge_queue(q->queues[i]); for (i = oldbands; i < q->bands; i++) { q->queues[i] = queues[i]; -- 2.39.5